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Tract tracing techniques combined with immunohistochemistry in rats and guinea pigs have demonstrated the existence of a hypothalamo-lateral septum enkephalinergic pathway. Numerous enkephalinergic nerve endings encompass cell bodies located in the lateral septum. The present immunocytochemical study, at light and electron microscopic levels, was undertaken in the guinea pig brain to determine whether the contacted perikarya contain γ-aminobutyric acid (GABA). The antisera against GABA revealed the presence of immunoreactive cell bodies throughout the lateral septum. At the light microscopic level, most GABA neurons appeared round while others were oval with one or two emerging dendrites. Ultrastructurally, cell bodies displayed a moderate number of organelles and a pale nucleus with frequent indentations of the nuclear envelope. The precise relationship between GABA neurons and enkephalinergic terminals was examined by means of a double-immunostaining method showing that 60% of cell bodies receiving synaptic inputs from enkephalinergic afferents contained GABA. These results show that the hypothalamo-septal enkephalinergic pathway prominently innervates GABA-containing neurons and also provide anatomical basis suggesting a disinhibitory role for this enkephalinergic tract.

This study assesses the action of hypercortisolism on the hormone and peptide periadenoma region of removed ACTH-producing microadenoma. Our findings show that cortisol excess affects both ACTH and GH production, with no immunoreaction for these hormones. The remaining pituitary hormones (TSH, FSH and PRL) and POMCderived peptides (ßEnd, aMSH and ßMSH) were not modified. Likewise, we observed pituitary immunoreactive cells for Neurotensin (NT), Intestinal vasoactive peptide (VIP), Substance P (SP) and Angiotensin-II (Ang-II). The colocalization demonstrated that NT was expressed in thyrotrope and gonadotrope cells, VIP in gonadotrope cells and SP in corticotrope cells. The results about Ang-II were inconclusive. On the other hand, immunoreaction for the NPY and Gal peptides were not present. In the adenomatous cells, the peptide NT is present in ACTH cells as well as SP. These results suggest a peptide regulation of pituitary cells in the pathological state that can differ between normal and tumoural cells of the same pituitary.

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Using an indirect immunoperoxidase technique, the localization of somatostatin-28 (1-12)-like immunoreactive fibers and cell bodies in the auditory cortex of the cat (anterior, primary, secondary, temporal, ventral, ventroposterior, posterior and dorsoposterior auditory fields) was studied. In general, the distribution of SOM-ir structures is widespread in the auditory cortex of the feline. A high density of immunoreactive fibers as well as a low density of cell bodies containing somatostatin were observed in all the layers of the eight above-mentioned auditory fields. These data indicate that somatostatin-28 (1-12) could act as a neurotransmitter and/or a neuromodulator in the auditory cortex of the cat. The origin of the SOM-ir fibers in the auditory cortex of the cat, as well as the issue of whether the cell bodies containing somatostatin-28 (1-12) are local or projecting neurons is discussed.

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Background Using an indirect immunoperoxidase technique, we have studied the distribution of immunoreactive fibers and cell bodies containing neurokinin in the adult human brainstem with no prior history of neurological or psychiatric disease. Results Clusters of immunoreactive cell bodies and high densities of neurokinin-immunoreactive fibers were located in the periaqueductal gray, the dorsal motor nucleus of the vagus and in the reticular formation of the medulla, pons and mesencephalon. Moreover, immunoreactive cell bodies were found in the inferior colliculus, the raphe obscurus, the nucleus prepositus hypoglossi, and in the midline of the anterior medulla oblongata. In general, immunoreactive fibers containing neurokinin were observed throughout the whole brainstem. In addition to the nuclei mentioned above, the highest densities of such immunoreactive fibers were located in the spinal trigeminal nucleus, the lateral reticular nucleus, the nucleus of the solitary tract, the superior colliculus, the substantia nigra, the nucleus ambiguus, the gracile nucleus, the cuneate nucleus, the motor hypoglossal nucleus, the medial and superior vestibular nuclei, the nucleus prepositus hypoglossi and the interpeduncular nucleus. Conclusion The widespread distribution of immunoreactive structures containing neurokinin in the human brainstem indicates that neurokinin might be involved in several physiological mechanisms, acting as a neurotransmitter and/or neuromodulator.

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The distribution of galanin-like immunoreactive fibers and cell bodies has been studied in the cat brainstem. Perikarya containing galanin were only found, at a low density, in the nucleus of the brachium of the inferior colliculus and in the pericentral nucleus of the inferior colliculus. The highest density of immunoreactive fibers was found in the laminar spinal trigeminal nucleus and in the parvocellular division of the alaminar spinal trigeminal nucleus. A moderate density of immunoreactive fibers was observed in the periaqueductal gray, locus coeruleus, marginal nucleus of the brachium conjunctivum and below the facial nucleus, whereas a low density of such fibers was found in the nucleus of the brachium of the inferior colliculus, pericentral nucleus of the inferior colliculus, nucleus incertus, medial division of the dorsal nucleus of the raphe, accessory dorsal tegmental nucleus, Kölliker-Fuse nucleus, lateral tegmental field, postpyramidal nucleus of the raphe, pericentral division of the dorsal tegmental nucleus, infratrigeminal nucleus, medial nucleus of the solitary tract, spinal trigeminal tract, dorsal motor nucleus of the vagus, and in the lateral reticular nucleus. According to the distribution of galanin-like immunoreactive structures in the cat brainstem, our data suggest that the peptide could be involved in respiratory, cardiovascular, nociceptive and auditory mechanisms.

The brain of the sturgeon has recently been shown to contain at least two forms of GnRH : mammalian GnRH and chicken GnRH-II. In this study, we compared the distribution of immunoreactive mGnRH and cGnRH-II in the brain of immature Siberian sturgeons., Il a été récemment démontré que le cerveau de l'esturgeon contenait au moins deux formes de GnRH : la GnRH de mammifère et la GnRH-II de poulet. Dans cette étude, nous avons comparé la répartition de la GnRH de mammifère et de la GnRH-II de poulet dans le cerveau de jeunes esturgeons de Sibérie.